1. Field of the Invention
The present invention relates to the field of illumination, and more particularly to a white light emitting diode module capable of using a stacked double chip to mix red phosphor to achieve high color saturation.
2. Description of the Related Art
Since light emitting diode (LED) has the advantages of low working voltage, small power consumption, high stability, long life, strong impact and vibration resistance, light weight, small volume and low cost, therefore the LED has been used extensively in many areas. In daily life, most of us use white light lamps for indoor illumination, so that the study of white light emitting diode has become an important subject.
At present, there are two main methods of producing a white LED as described below. 1. A combination of red, green and blue LEDs is used to produce a mixed light to obtain a white light source. 2. An LED light source is used to excite an illuminescent material to produce white light. For example, a blue LED together with phosphor that produces yellow light, or a blue LED together with two kinds of phosphors that produce green light and red light respectively, or a purple or ultraviolet LED that excites red, green and blue phosphors is used for producing white light.
Wherein, three chips (RGB) are packaged into an LED set. Although the white light produced by mixed lights has a relatively large color gamut and a good mixing light efficiency, the driving current of each chip can be adjusted freely to produce different colors. However, it is not easy to control the proportion of red, green and blue mixing lights, and the extent of the light emitting efficiency of each color being affected by temperature varies, and the life cycle of different chips varies, and the manufacturing cost is high, so that the aforementioned white light mixing method is not popular in the application of illumination.
Although the way of using a blue LED to excite yellow phosphor can produce white light, the chromaticity of the produced white light is poor and cannot be compared with the conventional incandescent lamp and cold cathode fluorescent lamp (CCFL). In addition, the way of using an ultraviolet LED to excite red, green and blue fluorescent lights to produce white light can produce a white light with high chromaticity. Since the light emitting efficiency of the ultraviolet LED is low and the ultraviolet power is high and the packaging material of LED may be aged easily, therefore this method cannot be applied in general illumination or a backlight modules.
Therefore, it is an urgent subject for the market to provide a design of a white light emitting diode module capable of simplifying the wire bonding process, lowering the cost, providing high color saturation, and improving the white light mixing effect.